Anatomy Atlas and Interpretation of Spine Surgery

6
J.-g. Shi et al.
2 Anterior Atlantoaxial Exposure by
Transmandibular Approach
2.1 Overview
Although exposure of the lower cervical spine is quite limited
through the transoral approach, the clivus to upper cervical
spine can be extensively exposed by a more complex
approach involving jaw splitting. Ever since the introduction
of the transmandibular approach by Martin in 1961, more
surgeons have reported different approaches to anterior craniocervical
junction. Wood et al. reported an expanded surgical
approach involving the splitting of the soft and hard
palates in addition to mandibulo glossotomy in 1980.
Delgado et al. reported a case of chordoma resection from
the clivus and upper cervical spine by mandibulotomy in
1981. Advantages of transmandibular approach include
simultaneous exposure of the upper and lower (abdominal
level) cervical spine, absence of major vessels and nerves,
and avoidance of lateral retraction of important structures.
However, extensive oropharyngeal swelling and infection
are the main concern of postoperative management. The
transmandibular approach is mainly used for the treatment of
benign and malignant tumors in the ventral midline of the
spinal cord, as well as congenital and posttraumatic deformities
in the craniocervical junction.
2.3 Exposure
Mental foramen: usually located underneath the root
of the second premolar tooth, at the midpoint between
the superior and inferior borders of the mandible, and
is about 2.5 cm lateral from the midline. The mental
foramen opens backward, upward, or outward, with
mental nerves and arteries passing through.
Mental nerve: terminal branch of the inferior alveolar
nerve. It enters through the mental foramen into the
face and innervates the skin of lower lip.
Mental artery: branches from the first segment of
maxillary artery and the terminal branch of the inferior
alveolar artery. It enters the face through the mandibular
canal from the mental foramen and supplies blood
to the muscle and skin of the mandible region.
2.2 Position
Patient is placed in supine position, and the head of the
patient maintains traction with slight extension
(Fig. 1.8).
Fig. 1.8 Anterior atlantoaxial exposure by transmandibular approach